Encoder-decoder device for selective calling



Dec. 24, 1968 A. N. FISCHER 3,418,577

ENCODERDECODER DEVICE FOR SELECTIVE CALLING Filed Nov. 7, 1963 l M4K@ 3,418,577 ENCODER-DECODER DEVICE FOR SELECT IVE CALLING Alfred N. Fischer, North Tonawanda, N.Y., assigner, by

mesne assignments, to Perry Laboratories, Inc., a corporation of New York Filed Nov. 7, 1963, Ser. No. 322,197 4 Claims. (Cl. 325--18) This invention relates to a combination encoder-decoder for selective calling and receiving in connection with twoway radio transmission.

In recent years, combination transmitters and receivers, frequently known as transceivers, have come into rather common use. One reason for this is the so-called citizens band unit of rather low power which can be used by those who are not skilled in the art of radio communications.

In citizens band transmission, there is necessarily a large number of transmitters and receivers operating on the same frequency. It is obviously undesirable for any one receiver to intercept all messages which are not intended for it. It is also undesirable for one to have to hear the various noise signals which would be promulgated by the loudspeaker of a receiver if the receiver were switched in operative condition at all times.

Accordingly, it is desirable to have the loudspeaker of a receiver normally inoperative, and to be rendered operative only upon receiving a call intended for the particular receiver.

In view of the foregoing, it is an object of the present invention to provide a combination encoder-decoder unit for selective calling or receiving on two-way radio.

Furthermore, it is an object of this invention to provide an encoder-decoder unit operating with a two-tone code, thereby substantially eliminating the possibility of accidental operation.

It is another object of this invention to provide a combination encoder-decoder unit which is easily connected to existing transceiver equipment for operation in conjunction therewith.

Specifically, it is an object of this invention to provide a combination encoder-decoder unit utilizing a plurality of vibrating reeds as frequency selective calling and receiving devices.

It is yet another object of this invention to provide in a combination encoder-decoder unit a reed relay unit in which the reeds are plucked electromagnetically yby application of a potential to a coil means, following which the coil means has a coded signal induced therein in accordance with the vibration of the reeds.

Additionally, it is an object of this invention to provide a reed relay device in a combination encoder-decoder unit which reed relay device has a pair of coils wound on a common core, and a plurality of tuned vibratile reeds in inductive relation with both of said coils.

Yet another object of the present invention is to provide a combination encoder-decoder unit involving relay switching wherein means is provided for overcoming physical shocks to hold the relay in normally open position.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a top view of the reed relay device in somewhat schematic fashion;

FIG. 2 is a side view thereof;

FIG. 3 is a circuit wiring diagram of the combination encoder-decoder unit; and

FIG. 4 s a fragmentary wiring diagram demonstrating lUnited States Patent O ICC a typical audio output circuit of a transceiver to which the unit of FIG. 3 is to be connected.

Reference rst should be had to FIGS. 1 and 2 for a general understanding of the resonant reed relay device in question. In these two figures, there is shown a resonant reed relay device 10 comprising a frame 12 of nonmagnetic material which in vertical section is generally I- shaped. A sheet metal pole piece of steel or other suitable magnetic material upstands at 14 from an integral magnetic base 16 lying along the top of the bottom portion of the frame 12. Coil means 18 is wound on the pole piece 14, and as will appear presently, this coil means comprises a pair of coil windings.

A permanent magnet 20 of generally cylindrical form is mounted on the base 16 by means such as a screw 22 passing through an L-shaped sheet steel or other magnetic material member 24 having an upstanding portion 26.

A plurality of vibratile resonant reeds 28 is mounted by suitable insulating means 29 from the upper portion of the frame 12 with the free ends thereof extending above the pole piece 14. Flexible contact members 30 are secured respectively above the reeds 28, and are biased into proper position by set screws 32 passing through an insulating member 34 secured to the upper portion of the frame. The reeds are electrically connected in common to a terminal 36, while the contact strips 30 are individually provided with electrically isolated terminals 38, 40, 42 and 44.

Means also preferably is provided for selectively physically restraining the reeds, and this is shown in phantom in FIGS. 1 and 2 as an elongated member 46 extending across the upper surfaces of the free ends 0f the reeds, and provided with suitable cam-like projections for individually or collectively restraining the reeds. Further details on such structure can be found in my co-pending application, Ser. No. 227,319 filed Oct. 1, 1962, and entitled, Selectable Multi-Channel Resonant Reed Relay.

Referring now to the circuit diagram of FIG. 3, the coil means 18 will be seen to comprise a low impedance coil 48 and a high impedance coil 50. Both coils are wound on the pole piece 14, and one end of each coil is grounded as indicated at 52.

The unit, hereinafter identied by the numeral 54, further comprises a four-pole, triple-throw switch 56. The various switch sections and the movable contacts thereof are respectively indicated at SA, SB, SC and SD, all being ganged together as indicated at 58. Each of the switch sections has three positions, i.e., three fixed contacts, as indicated by the numerals 1 through 3 in the four positions.

The ungrounded end of the low impedance winding 48 is connected by means of a wire 60 to a voltage regulator 62 in the form of a pilot lamp which is painted black. The lamp may, for example, be a type G-l2. The opposite side of the regulator 62 is connected to the slider or movable contact at switch section SC.

The high side or ungrounded end of high impedance winding 50 is connected by ymeans of a wire 64 to xed contacts 2 of the switch section SB. It further is connected by a wire 66 to the movable contact of switch section SD.

The common reed tenminal 36 `is connected through an integrating network comprising a series resistor 68 and capacitor 70 to ground. The capacitor is by-passed by a resistor 72 to bleed od a charge on the capacitor. For a specific example, the resistor 68 may be taken as 1,000 ohms, the resistor 72 as 2.7 megohms, and the capacitor 70 as .l microfarad.

Reference heretofore has been made to the connections to the movable switch contacts of switch sections SC and SD. The movable contact of switch section SA is grounded. The movable contact of switch section SB is unconnected, but it is of a type that momentarily shorts fixed contact 2 to fixed contact 3 as the switch 55 is moved from position 2 to position 3.

As shown in FIG. 3, the upper and lower reeds 28 are connected. It is to be understood that the other two reeds are physically restrained against vibration. However, it will be understood that any two reeds could be connected, with the other two reeds restrained against vibration, and the combination of various active reeds allows several combinations of call signals to be established. As shown in the drawings, the shortest or upper reed 2S is connected by a wire 74 to a resistor 76 leading to a B+ bus 78. This bus is connected by a wire to the B+ supply of the transceiver. Conveniently this connection is made by a plug and socket type of device, not shown. The B+ bus `iS connected through a resistor 82 and a pair of neon pilot lights 84 and 86 to ground. For exemplary purposes, the resistor 76 may be taken as 6800 ohms, or the resistor 82 may be taken as 47,000 ohms.

The lower or longest reed 28 is connected to -a junction 88. This junction is connected to a resistor 90, which in turn is connected to a capacitor 92, the opposite side of the capacitor being connected to a line 94. The line is connected at 96 to iixed contact 1 of switch section SA. The line 94 also is connected to one end of the winding 98 of a relay 100. The opposite end of the winding is connected by a wire 102 back to the junction 88. The wire 102 also is connected through a neon bulb 104 to the junction 106. The junction is connected by a resistor 108 to the B+ bus 78.

For exemplary purposes, the resistor may be taken as 1,000 ohms, and the capacitor 92 as .22 microfarad, and the resistor 108 as 6800 ohms.

The relay is provided with an upper fixed contact z 110 and a lower fixed contact 112, a mov-able contact 114 alternately engageable therewith. The Contact 114 in a normal position engages the contact 110, and moves out of contact with the contact 110 into engagement with the contact 112 upon energization of the relay 100.

The upper fixed contact 110 is connected by means of a wire 116 to a wire 118 leading to the junction 106. It further is connected to a capacitor 120 which leads to a wire 122 to the movable contact 114. The capacitor 120 may be considered, for exemplary purposes, as .047 microfarad.

Movable contact 114 is connected to ground. The lower iixed contact 112 is connected by a wire 124 to junction 126, the latter being connected by a wire 127 to xed contact 2 of switch section SA, and by a wire 128 to the bottom end of a potentiometer resistor 130. The fixed contract 112 also is connected by a capacitor 132 to ground, this capacitor, for example, being .0l microfarad. Potentiometer 130 is a speaker volume control.

The opposite end of the potentiometer resistor 130 is connected at a junction 134 to a wire 136 leading to fixed contact 1 of switch section SC. The junction 134 further is connected to a wire 137 leading to the high side of the output transformer of the transceiver.

The sliding cap 138 on the potentiometer resistor is connected to a junction 140, and from there to a wire 142 to the speaker terminal A, hereinafter to be discussed. Junction further is connected by a resistor 144 to the wire 137, the resistor for example being 4.7 ohms.

The first and second fixed contacts of the switch section SA have previously been described as to their connections. The third fixed contact is connected fby means of a wire 145 to a transmit switching line leading to the transceiver.

In switch section SB, the first switch contact is not connected to anything. The second contact has been discussed, and contact 3 is connected by means of a wire 146 to a resistor 148 shunted by za capacitor 150, the resistor in turn being connected bv means of a wire 152 to the B+ bus 78.

CTI

The connection to contact 1 of switch section SC has been discussed. Contacts 2 and 3 are not connected.

Contact 1 of switch section SD is grounded through a resistor 154. For exemplary purposes, this resistor may be considered to be 15,000 ohms, the resistor 148 may 'be considered to be 470,000 ohms, and the capacitor 150 may be considered to be .047 microfarad.

Switch contact 3 of switch section SD is connected by a wire 156 to a :capacitor 158, and this capacitor by way of example may be .0l microfarad. The opposite side of the capacitor is connected to the center shielded conductor 160 of a microphone amplifier input, the slee-ve being shielded Vby a grounded braid or the like 162.

Reference now should be had to FIG. 4 for a typical audio output circuit on a transceiver. Thus, there is the usual audio output transformer 164, having input wires 166, and output wires 168 and 170. The wire 168 is connected to speaker terminal A, While speaker terminal B is connected to a wire 172.

One of the lead wires at the right side of FIG. 3 has been labeled Speaker Terminal A and is connected to speaker terminal A of the transceiver. In transceivers where the wire 172 is connected to ground, and speaker switching is accomplished by grounding the wire 170, the wire 172 must be lremoved from ground; and this wire is then connected to the wire at the right of FIG. 3,

' labeled Speaker Terminal or Output Transformer.

In some transceivers, the wire 170 is connected to ground, and speaker switching is accomplished by grounding the wire 172. Rewiring is the same, wire 170 being removed from ground, and connected to the wire in FIG. 3 labeled Speaker Terminal or Output Transformer.

The position of the switch 56 determines the condition of the combination encoder-decoder unit, which might correctly also lbe referred to as a squelch unit. In the standby condition, the switch is turned so that the various movable contacts thereof are in contact with the No. 1 fixed contact. In the No. 2 position, the unit is in normal condition, while in switch position No. 3, the unit is in call condition.

In the call or transmit position, the reed relay is used to generate preselected audio tones. In the standby position, the reed relay is used to detect the presence of preselected audio tones.

In the normal position, the speaker ground return is grou-nded as just discussed in connection with FIG. 4. `In particular, either the lwire 170 or the wire 172 is connected to the wire at the right of FIG. 3 labeled Speaker Terminal or Output Transformer. This may be followed through wire 124, junction 1126 and wire 127 to contact 2 of switch section SA, and it will be seen that with the switch in normal position, ground is applied to the line 127. Accordingly, the transceiver is in condition for normal operation.

In the event that it is decided to call another transciever on the same channel, and with the same calling code, the switch is turned to position 3. Contact 3 of switch section SA thus is grounded to connect the transmit switching line to ground, and thereby to turn on the transmitter.

Switch section SB momentarily shorts Contact 2 to contact 3. This allows the capacitor 150 to charge quickly to B+ potential through the B+ bus 7S and wire 152, and further through 'wire 146, contacts 2 and 3, wire 64, and coil 50 of relay 10 and wire 52 to ground. This pulls the reed in toward the coil and toward the pole piece 14. The contact from 2 to 3 is made only momentarily, land the capacitor 150 quickly charges. Thus, the current through the high impedance coil 50 is of limited duration, and as soon as it has decayed, the reeds are released and vibrate. It will be apparent that this is thy a plucking action.

Vibration of the reeds in proximity to the pole piece 14 and coil 50 induces current in the coil at the natural period of vibration of the two reeds which are free to vibrate. Such currents are transmitted through the wire 64 and wire 66 to switch section SD, and particularly to contact 3 thereof, and hence out through the microphone amplifier input, thereby to put a coded signal on the transmitter corresponding to the frequencies of the two vibrating reeds.

Switch section SC can be ignored at this time, as it is on a non-connected contact.

When the switch is in position 1 for receiving a call from another unit, the speaker ground return is disconnected, the switch section SA being on terminal .1, rather than contact 2. Hence, no sound is heard over the speaker, and the party having the transceiver need not listen to various noise signals and to other transmissions on his channel. The relay 98 and integrating network comprising resistor 90 and capacitor 92 are grounded.

Switch section SB may -be ignored, since it is on a nonconnected contact. Switch section SC connects the high side of the output transformer through the limiter 62 to the low impedance coil 48 of the reed unit 10. The resistance of the lamp used as a limiter 62 varies with the current through it, and hence lrnaintains the voltage applied to the low impedance winding 48 constant. Uniformity of voltage across the winding 48 also is `effected by transformer action coupling to the high impedance winding 50. This winding is connected through the wires 64 and 68 land switch section SD to grounded resistor 154. Transient peaks are substantially eliminated by the connection to the resistor 154.

Imposition of a calling signal comprising two reed frequencies on the coil 48 causes the corresponding reeds to vibrate. In the particular example shown and described, this comprises the upper and lower reeds. Capacitor 70 charges upon intermittent closure of the top reed with its contact. Resistor 72 bleeds off the charge rapidly, so that inadvertent or accidental closure of the reed and its contact in response to an accidental signal, or physical shock will not cause operation of the unit.

The charge on capacitor 70 is transferred upon intermittent closure of the bottom reed to the integrating network comprising resistor 90 and capacitor 92. When the voltage at this point has reached a high enough value, the relay 100 starts to pull in.

As soon as this relay starts to pull in, the movable contact 114 leaves the fixed contact 110, and the top of the neon bulb 104 at junction 106 immediately goes to B+ potential. The neon bulb fires and applies a higher voltage to the relay coil 98 to pull the relay in quickly. The relay then remains in the on position indefinitely, with the neon bulb 104 providing a visual indication that a call has been made.

Accidental closure of the relay is prevented by the capacitor 120 which acts as a dead short to hold the top of the neon bulb 104 at ground potential if a physical shock tends to open the contacts 110, 114.

Closure of the relay contact 114 on the contact 112 grounds the speaker terminal or output transformer line to render the speaker operative. Thus, the calling signal on the line 136 is transmitted to the potentiometer 130, 138 to speaker terminal A, and the signal is heard audibly on the loudspeaker to alert the called party so that he may answer. In the event that the party is not within earshot, he will upon return to his transceiver check the neon bulb 104, and see that he has received a call.

The capacitor 132 is provided as an RF bypass to prevent imposition of radio frequencies on the unit. Obviously, when a party has received a call as indicated above, he simply moves the switch 56 from standby position 1 to normal position 2. This effects the connection as heretofore described relative to position 2, and also removes the ground connection from the relay 100, whereby this relay returns to its normal position.

It will be apparent that two reeds are simultaneously actuated in accordance with the foregoing description. A suggestion has been made that such deactivation might be effected by a cam-like damping structure. This particular physical construction is not a necessity with the present invention, and other restraining means could be used, such as a pair of plastic sleeves selectively slipped over two of the reeds.

lt will now be apparent that the objects of the invention have been satisfied, and that a rugged and inexpensive encoder-decorder unit has been provided. The specific example of the invention as hereinshown and described is for exemplary purposes. Various changes in structure will no doubt occur to those skilled in the art, and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. An encoder-decoder unit for use in combination with two-way radio apparatus, said unit comprising tuned vibratory reed means having at least two reeds of different natural frequencies of vibration and a coil simultaneously in inductive relation to both of said reeds, said reeds being electrically connected together, at least two fixed contacts respectively engageable by said reeds upon vibration thereof, a source of electric potential connected to one of said fixed contacts and not to the other, relay means connected to the other of said fixed contacts, said reeds upon vibration being electrically in series between said potential source and said relay means, connection means for connection to such two-way radio apparatus, switch means, means selectively interconnecting said switch means and said connection means with said switch means in one position for rendering said radio apparatus operative in its normal fashion, means selectively interconnecting said switch means, said coil and said connection means with said switch -means in another position to transmit a coded signal by said radio apparatus upon substantially simultaneous vibration of both of said reeds, means for substantially simultaneously vibrating both of said reeds to induce a signal code in said coil, and means interconnecting said connection means, said switch means, said coil and both of said reeds in a further position of said switch means with the loudspeaker of said radio apparatus rendered inoperative to effect substantially simultaneous vibration of both of said reeds in response to receipt by said radio apparatus of a coded signal, and means including said relay means effective upon such vibration to render the loudspeaker of said radio apparatus operative.

2. An encoder-decoder unit for use in combination with two-way radio apparatus, said unit comprising tuned vibratory reed means having at least two reeds of different natural frequencies of vibration and a coil simultaneously in inductive relation to both of said reeds, connection means for connection to such two-way radio apparatus, switch means, means selectively interconnecting said switch means and said connection means with said switch means in one position for rendering said radio apparatus operative in its normal fashion, means selectively interconnecting said switch means, said coil and said connection means with said switch means in another position to transmit a coded signal by said radio apparatus upon substantially simultaneous vibration of both of said reeds, means for substantially simultaneously vibrating both of said reeds to induce a signal code in said coil, and -means interconnecting said connection means, said switch means, said coil and both of said reeds in a further position of said switch means with the loudspeaker of said radio apparatus rendered inoperative to effect substantially simultaneous vibration of both of said reeds in response to receipt by said radio apparatus of a coded signal, and means including a relay for rendering the loudspeaker effective upon such vibration, the ground return of the loudspeaker being open with the relay in its normal position and being closed upon operation of the relay, said relay having an operating coil, and said encoder-decorder unit further including a source of holding potential for said relay, a resistor connected to said source of holding potential, a gas diode connected between said resistor and said relay coil, said relay having a movable contact alternately engageable with first and second xed contacts, said movable contact being grounded and normally being connected to said first fixed contact, means connecting said first fixed contact between said gas diode and said relay whereby normally to hold said gas diode in non-conducting condition, said diode being rendered conductive upon movement of said movable contact away from said first fixed contact whereby to apply a holding potential to said relay coil, said second fixed Contact being interconnected with said connection means to render the loudspeaker effectve upon engagement of the movable contact with the second fixed Contact.

3, In a switching unit for use in combination with radio apparatus, the combination comprising a resonant reed relay having vibrating reed means and coil means in inductive relation therewith, a source of potential, a switching relay having a coil and having a movable contact and at least one fixed contact with which said movable contact is normally in engagement, resistor means connected to said source of potential, a normally non-conductive gas diode connected between said resistor means and said relay coil for holding said relay energized, means connecting said source of potential to said resonant reed relay reed means, means effecting a connection from said reed means upon vibration thereof to said relay coil t0 apply operating potential thereto, and means for applying a coded signal to said resonant reed relay coil means to effect vibration of said reed means, said relay movable contact `being grounded, said fixed contact being connected lbetween said resistor and said gas diode, movement of said movable contact away from said fixed contact removing ground potential from between said gas diode and said resistor to effect firing of said gas diode to apply holding potential to said relay coil.

4. A switching unit as set forth in claim 3 and further including a capacitor connected from the junction between the resistor and the gas diode to ground to prevent firing of said gas diode upon inadvertent momentary opening of said movable and fixed contacts.

References Cited UNITED STATES PATENTS 2,247,324 6/1941 Travis 325-482 2,630,482 3/1953 Bostwick 333-71 X 3,123,675 3/1964 Boone et al. 179-87 3,292,085 12/1966 Black 340-171 X 2,524,782 10/1950 Ferrar et al. 325-64 X 2,579,470 12/1951 Brown 325-55 X 3,040,256 6/1962 Bostwick et al. 343-228 X 3,138,755 6/1964 Kompelien 325-55 X 3,210,665 10/1965 Street 325-55 X 3,250,997 5/1966 Cole et al. 325-64 X ROBERT L. GRIFFIN, Primary Examinez'.

B. V. SAFIYREK, Assistant Examiner.

U.S. Cl. X.R. 

1. AN ENCODER-DECODER UNIT FOR USE IN COMBINATION WITH TWO-WAY RADIO APPARATUS, SAID UNIT COMPRISING TUNED VIBRATORY REED MEANS HAVING AT LEAST TWO REEDS OF DIFFERENT NATURAL FREQUENCIES OF VIBRATION AND A COIL SIMULTANEOUSLY IN INDUCTIVE RELATION TO BOTH OF SAID REEDS, SAID REEDS BEING ELECTRICALLY RELATION TO BOTH OF SAID REEDS, SAID FIXED CONTACTS RESPECTIVELY ENGAGEABLE BY SAID REEDS, SAID VIBRATION THEREOF, A SOURCE OF ELECTRTIC POTENTIAL CONNECTED TO ONE OF SAID FIXED CONTACTS AND NOT TO THE OTHER, RELAY MEANS CONNECTED TO THE OTHER OF SAID FIXED CONTACTS, SAID REEDS UPON VIBRATION BEING ELECTRICALLY IN SERIES BETWEEN SAID POTENTIAL SOURCE AND SAID RELAY MEANS, CONNECTION MEANS FOR CONNECTION TO SUCH TWO-WAY RADIO APPARATUS, SWITCH MEANS, MEANS SELECTIVELY INTERCONNECTING SAID SWITCH MEANS AND SAID CONNECTION MEANS WITH SAID SWITCH MEANS IN ONE POSITION FOR RENDERING SAID RADIO APPARATUS OPERATIVE IN ITS NORMAL FASHION, MEANS SELECTIVELY INTERCONNECTING SAID SWITCH MEANS, SAID COIL AND SAID CONNECTION MEANS WITH SAID SWITCH MEANS IN ANOTHER POSITION TO TRANSMIT A CODED SIGNAL BY SAID RADIO APPARATUS UPON SUBSTANTIALLY SIMULTANEOUS VIBRATION OF BOTH OF SAID REEDS, MEANS FOR SUBSTANTIALLY SIMULTANEOUSLY VIBRATING BOTH OF SAID REEDS TO INDUCE A SIGNAL CODE IN SAID COIL, AND MEANS INTERCONNECTING SAID CONNECTION MEANS, SAID SWITCH MEANS, SAID COIL AND BOTH OF SAID REEDS IN A FURTHER POSITION OF SAID SWITCH MEANS WITH THE LOUDSPEAKER OF SAID RADIO APPARATUS RENDERED INOPERATIVE TO EFFECT SUBSTANTIALLY SIMULTANEOUS VIBRATION OF BOTH OF SAID REEDS IN RESPONSE TO RECEIPT BY SAID RADIO APPARATUS OF A CODED SIGNAL, AND MEANS INCLUDING SAID RELAY MEANS EFFECTIVE UPON SUCH VIBRATION TO RENDER THE LOUDSPEAKER OF SAID RADIO APPARATUS OPERATIVE. 